The present invention relates to a lightweight, collapsible, easily transported apparatus for checking the geometry of a vehicle's frame and axles. While the preferred embodiment is shown being used to check the vehicle geometry of a tractor/trailer rig, it will be apparent to those skilled in the art that with insignificant alterations the preferred embodiment may be used for checking the vehicle geometry of smaller or larger vehicles also.
A vehicle's frame and axle geometry may be evaluated with regard to parallelism of frame rails and axles, and perpendicularity of axles with regard to frame rails. While the vehicle manufacturers' specifications should be consulted regarding the designed angular relationships of frame members and axles, it will be assumed for the purpose of describing the preferred embodiment of the invention that the frame rails extending from front to rear of a tractor or trailer are designed to be parallel to each other, and that all axles of the tractor and trailer are designed to be parallel to each other and perpendicular to the frame rails. A significant deviation from parallelism or perpendicularity may result in vehicle tracking problems, adversely affecting fuel economy, ride and handling, as well as poor tire wear characteristics.
While various methods and apparatus for checking vehicle geometry have been devised, most rely upon the person doing the checking being able to use a variety of instruments, often designed for other purposes, such as steel squares, straight edges and yard sticks, making measurements of vehicle geometry awkward.